1. Field of the Invention
The present invention relates generally to mechanical mounting arrangements and, in particular, to a mechanical mounting system and extensional damping technique for loudspeaker crossover networks.
2. Description of the Relevant Art
Loudspeaker crossover networks (the electrical filtering and equalization circuitry of a loudspeaker) are very prone to low level intermodulation distortion effects when exposed to vibrational energy. This often becomes critical when the crossover networks are mounted within the loudspeaker cabinet where vibrational energy may be propagating freely though the cabinet walls and the interior air. Since most crossover networks are rigidly mounted to the cabinet walls, vibrational energy is directly coupled into the network. Energy coupled from the cabinet usually will travel though the network mounting screws, pc board or mounting board (if hard-wired) and into the electrical components themselves. It is also possible for vibrational energy in the internal air of the cabinet to be coupled either directly into the electrical components or through the pc board or mounting board into the components. The effects of this vibrational energy, when coupled into the electrical components, are typically manifested as a masking of low level detail and a subtle, but perceivable, intermodulation of the desired audio signal.
Manufacturers have attempted to address this problem in several different ways, including: (1) mounting the crossover networks outside of the loudspeaker cabinet; (2) encasing the crossover network in a highly damped potting compound; and (3) isolating the crossover networks within the cabinet by hanging them from wires or springs.
Mounting the loudspeaker networks outside of the cabinet offers improved performance since the cabinet walls and interior air of the loudspeaker can no longer couple vibrational energy into the networks. Unfortunately, vibrational energy can be coupled from the air in the listening environment (i.e., the loudspeaker's output energy) into the networks. Therefore, the networks still must be isolated in some manner from vibrational energy in the air. Mounting the networks outside of the cabinet usually will require an additional enclosure and its associated external wiring complications and additional electrical connections, as well as significant added cost.
Encasing the crossover networks in a highly damped potting compound can offer improved performance provided the damping characteristics of the potting compound are sufficient. However, this method has the disadvantages of poor heat dissipation from the network components, lack of repairability and high cost.
Other methods of isolation, such as hanging the networks, are usually either ineffective or overly complex. The effectiveness of hanging the networks is completely dependent upon the transmissibility characteristics of the hanging system (e.g., the wires or springs). The hanging system may not isolate adequately at all frequencies. In particular, if the hanging system resonance is too high, amplification of vibrational energy will occur, making the problem worse. A hanging system also does nothing about airborne vibrational energy within the cabinet. Hanging systems are also prone to shipping damage if the cabinet encounters rough handling.